Shock absorbing strut for aeroplanes



Patented July 18, 1933 UNITED STATES PATENT OFFICE RAYMOND L. GRUSS, DECEASED, LATE OF SAN FRANCISCO, CALIFORNIA, .BY LAURA E. GRUSS, ADMINISTRATRIX, OF SAN FRANCISCO, CALIFORNIA, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE CLEVELAND PNEUMATIC TOOL COMPANY, OF CLEVELAND,

OHIO, A CORPORATION OF OHIO Application filed September 9, 1929. Serial No. 391,430.

This invention resides in the provision of a simply constructed, light, strong and durable shock absorbing device which may be readily incorporated with the-running gear of an aeroplane and made to serve as a shock absorbing strut that will strengthen the running gear as well as positively and eltectively check the shocks, ars and rebound actions which are occasioned in taking off and in landing aeroplanes.

An object of the invention is to provide a shock absorbing strut of the character described which employs a compressible cushioning medium and a non-compressible fluid in a novel and efiective manner, to-- gether with such a construction and an arrangement of parts that the required cush- -ioning action will be provided over a longer range of movement of the parts of the shock absorbing device than is required with similar devices when applied to land vehicles.

A further object is to provide in a device of the character described a novel means for causing a reliable checking of the shock and rebound actions, which means includes telescoped cylinders; a plunger carried by one cylinder with its especially constructed head working in the. other cylinder, together with two mediums of control of the movements of these parts, one of which mediums will be a compressible yielding one to check and absorb violent shocks and jars, whereas the other medium will be a non-compressible fiuid and will hydraulically control the rebound action without detracting from the effectiveness of the shock cushioning medium.

With the above mentioned and other objects in view, the invention consists in the novel construction and combination of parts hereinafter described, illustrated in the accompanying drawing, and set forth in the claims hereto appended, it being understood that various changes in the form, proportion, size and minor details of construction within the scope of the claims may be resorted to without departing from the spirit or sacrificing any of the advantages of the invention.

In the drawing- Fig. 1 is a front elevation of an aeroplane of the monoplane type equipped with my improved strut,

Fig. 2 is a sectional View in elevation,

showing the details and interior construction of my improved strut when extended,

and

Fig. 3 shows the strut illustrated in Fig. 2 in its compressed condition.

In the present embodiment of my invention as illustrated 'in detail in the accompanying drawing, I show my improved strut in Figure 1 and 2 as having an uppercylinder 10 into which there telescopes a lower cylinder 11. The cylinder 11 carries a partial closing member 12 upon which there is maintained a suitable packing 13 which engages the inner wall of the cylinder 10 and the cylinder 10 carries a packing 14 which engages the exterior wall of the cylinder 11. When the cylinders are thus assembled they will ailord a liquid tight container which is adapted to hold a suitable non-compressible fluid 15, which in the present instance is preferably oil. At the top of the cylinder 10 there is provided in addition to an attaching means 16, an air inlet valve 17 through which air under pressure may be injected into the cylinder 10 above the oil 15. At the lower end of the cylinder 11 there is also provided an attaching means 18 similar to the attaching means 16. The attaching means 16 and 18, it will be understood, are provided for the purpose of maintaining the strut upon the cooperating parts of the aeroplane fuselage and running gear adjacent to the attaching means 18. There is also shown a drain plug -19 by which means the cylinder 10 may be drained in order to renew the oil therein. With the above arrangement of parts it will be seen that when the cylinder 10 has been charged with a pre-determined amount of air under pressure and thecylinder 11 filled with oil, as illustrated, that the parts will extend themselves to a point depending upon the amount of air pressure within the cylinder 10 and the weight being sustained. In other words, with an assembly as above described there willbe provided what might be termed a pneumatic Cushioning device air spring which will compress and extend in accordance with the forces applied thereto.

In order to provide a check against violent rebounding and recoil, I propose to provide a member 20 which is secured to the upper end of the cylinder 10 and extends axially downward therethrough to a point within the cylinder 11, and upon the end of the member 20 I provide a piston 21 which will function to check any tendency to rebound. The piston 21 is shown as provided with a plurality of openings 22 through which the oil 15 may flow freely and cooperating with the openings 22 there is shown a valve member 23 which operates somewhat after the fashion of a flap valve of a pump. This member 23, as will be readily understood, will function when in contact with the piston 21 to prevent a flow of oil through the openings 22 and in this manner it will restrict the flow of oil from above the piston 21 to the annular clearance space 21' between it and the walls of the cylinder 11, and thus act to check any sudden rebound or extension of the cylinders 10 and 11. This arrangement will at the same time permit a free flow of the oil 15 upwardly through the piston 21 so that full advantage may be taken of the elasticity of the air under pressure in the cylinder 10.

It will be readily appreciated that the member 20 might well be a solid rod but in the preferred embodiment, I propose to construct this member 20 of tubular material and provide near the upper end thereof suitable metering openings 24 through which the oil 15 may escape, as the cylinders 10 and 11 are compressed, so that in this manner provide an additional escape for the oil below the piston 21 when the pistons are being compressed. It will be noted that by reason of the location of the openings 24 that this passageway through the tubular member 20 will not interfere with the checking action of the valve member 23 as the cylinders 10 and 11 are extended. Upon examining the closure member 12 uponthe cylinder 11 it will be noted that it is provided with an inwardly extending flange 25 through the center of which the member 20' above, which will cooperate with the suction effect immediately therebelow in effectmg the recoil checking action of the piston 21. Attention is also directed to the fact that the opening in the partial closure member 12 is provided to accommodate the rod 20, and that this opening is slightly larger in diameter than the rod, thus forming an annular metering passageway 12. The

area of this passageway 12' is slightly less than the sectional area of the rod 20, so that it will permit a metered flow of the oil 15 from the lower cylinder 11 into the upper cylinder 10 as the parts telescope and as directly caused by the oil displaced by'the rod 20 as it is projected into the body of the oil 15 in the lower cylinder 11.

In Figure 3 of the drawing, the strut is shown as in its compressed position with the member 23 in the position it will assume at the end of the compression stroke. The member 23 is in the form of an annular disc which slides freely upon a collar 26 held between the piston 21 and a washer 27 which abuts a nut 28, there being an additional nut 29 upon the end of the member 20 for retaining the piston in this assembled.

position. Operation When my improved strut is mounted upon a plane as shown in Figure 1 of the drawing, it will be understood that when the plane is in the air the parts of the strut will assume the positions illustrated in Figure 2 of the drawing. This will mean that the wheels 30 will assume their lowermostposition and thus contact with ground will be made when the strut is most resilient. As the plane settles down and the wheels 30 take up the weight of the plane the strut will be compressed and the cylinder 11 .will telescope into the cylinder 10. The air pressure within the cylinder 10 will be increased by reason of its compression luitil the pressure is sufficient to carry the weight of the plane. From the above it will be seen that upon landing the complete shock caused by contact of the wheels 30 with the ground will be absorbed by the air cushion within the cylinder 10.

In addition to absorbing the shocks upon landing, my improved strut will also provide for easy riding while taxiing the plane over the landing field as it will not only provide an air cushion complementary to the usual tires but also provide an effective rebound or recoil checking means which will prevent excessive rebound.

The operation of the recoil or rebound checking means is as follows: As the parts are compressed the cylinder 11 with its oil 15 will move upwardly through and around the .piston head 21. During this movement the valve member 23 will assume a raised position which will permit the oil to flow through the metering openings 22 although this will produce a checking action since the combined area of the opening 22 and the annular passageway 21 is less than the area of cylinder 11 within which oil is displaced. Such would still be the case if the rod 20 is formed with a central passageway and with the by-pass openings 24. These openings not only permit oil to pass centrally of the rod and to be transferred from the cylinder 11 to the cylinder 10, but also break the vacuum seal which might occur in the cylinder 11 by allowing air from the cylinder 10 to pass downwardly into the body of oil if necessary, as the cylinder 11 moves upwardly. In operation of the structure, at the time the cylinder 11 telescopes within the cylinder 10 the piston 21 will move downwardly through the body of oil 15 as the oil is forced through the opening 22 and through the annular space 21 between the edge of the piston and the cylinder 11. This action will retard the relative movement of the two cylinders toward each other. The retarding action is further increased by" the restricted flow of oil through the annular passageway 12 as displaced by the rod 20. Upon the return stroke when the cylinders 10 and 11 move from their telescoping positions, the movement will be resisted due to the difliculty of the piston 21 passing through the fluid 15 in the cylinder 11, since at that time the valve member 23 will be closed and the piston will only be rmitted to move as oil flows around the piston through the annular passageway 21. When the plane rises or the wheels are suddenly brought out of con-' tact with the ground as due to a rebound the valve member 23 will, when the cylinders 10 and 11 tend to extend themselves, move downwardly upon the piston head 21 and thus close the openings 22 therethrough so that any sudden extension of the cylinders 10 and 11 will thus be prevented.

It will thus. be seen that the structure here disclosed provides means operating in conjunction with an aeroplane landing gear to permit the plane to easily alight without imparting objectionable vibration from the landing gear to the plane and while absorbing the shock of impact, and that the structure will also act to readily resist rebound by simple and effective means.-

While I have shown the preferred form of my invention as now known to me, I desire to have it understood that various -Wardly projecting tubular rod attached at its upper end to said first c linder arranged concentrically within said rst cylinder and telescoping with said second cylinder, said downwardly projecting tubular rod being open at its lower end and'having a restricted opening in its upper end, packings carried by said first and said second cylinders for comprising a downwardly projecting open ended cylinder adapted to be attached to the aeroplane structure, an upwardly projecting open ended cylinder adapted to move within said first cylinder and be attached to the running gear of the aeroplane, packings arrange at the open ends of said cylinders adapted to cooperate with the walls thereof, and retain a compressible and non-compressible fluid within said 0 linders, a tubular rod secured to the top oi said first cylinder and extending downwardly therethrough andinto said second cylinder, said tubular rod being open at its lower end and having a vent opening adjacent its upper end to permit constant restricted flow of fluid through the tubular rod, and a valve element mounted u on the extended end of said tubular rod isposed within said second cylinder adapted to restrict the flow of liquid within the second cylinder and therethrough in one direction so as to retard the movement of said second cylinder in one direction.

3. A shock absorbing strut for aeroplanes comprising a downwardly projecting open ended cylinder adapted to be attached to the aeroplane structure, an upwardly projecting open ended cylinder adapted to move within said first cylinder and be attached to the running gear of the aeroplane, packings arranged at the open ends of said cylinders adapted to cooperate with the walls thereof, and retain a compressible fluid within the upper cylinder, and non-compressible fluid within said lower cylinder, 2. cylinder head member at the open end of said second cylinder having an opening centrally therethrough forming a restricted passageway for said non-compressible fluid, and a valve element disposed within said second cylinder and through which the non-compressible fluid within the lower cylinder may flow and is adapted to cooperate with said restricted opening to retard movement of said second cylinder in one direction.

4;. A hydro-pneumatic shock absorbing strut for aeroplanes comprising a downwardly projecting open ended cylinder adapted to be attached to the aeroplane structure, an upwardly projecting open ended cylinder adapted to move within said first cylinder and be attached to the running gear of the aeroplane, packing means interposed between said telescoping cyl- -inders,'a c linder head member at the open said second cylinder and a valve element carried by said piston through which noncompressible fluid within the second cylinder may flow, said valve element being adapted to cooperate with said restricted opening to retard movement of said second cylinder in.

one direction.

- LAURA E. GRUSS, Administmzfm'a: of the Estate of Raymond L.

Grass, Deceased. 

